Channel Hopping is a mechanism by which a transmitter ‘hops’ through or moves to different channels (frequency bands) during its normal operation. A data exchange between nodes may happen on a single channel or multiple channels depending on the different protocols. Although nodes hop on multiple channels, a single transmission and reception happens only on one of those channels. The channel hopping increases network throughput by promoting simultaneous data transfer over multiple channels between different pairs of nodes and improves reliability in rough channel conditions by exploiting the channel diversity.
One application of channel hopping is Frequency Hopping Spread Spectrum (FHSS). FHSS is a method of transmitting radio signals by switching carriers among many frequency channels using a pseudorandom sequence known to both transmitter and receiver. In such systems, signal transmitters rapidly switch carrier frequencies using various “hopping” schemes to avoid the problem of signal interference at a particular frequency. However, for such systems to operate, the TX and RX pair have to align on the spreading sequence to be used as it requires PHY level synchronization.
Other methods to achieve channel hopping involves changing of channel at PHY level as directed by MAC. However, a single frame exchange is performed only on one channel or few channels. Frequency hopping allows transmitting devices to use various carrier frequencies to enhance the signal transmission in various different transmission environments. In frequency hopping systems, signals experience different sets of interference during each “hop” and thus avoid possible constant interference at a particular frequency. Frequency hopping is commonly used for transmission in Wireless Local Area Networks (WLAN), Global System for Mobile Communications (GSM), Bluetooth, and various other communication systems. Channel hopping wireless transmission system protocols typically have a retransmission mechanism to retransmit lost packets. When channel hopping is used, subsequent retransmissions can use a different channel in the channel hopping sequence. This helps avoiding channel interference that may have existed in the previous channel causing the packet loss.
Channel hopping can be achieved through many different implementations. Some of the common implementations include synchronous method such as Time Slotted Channel Hopping (TSCH) or asynchronous method such as un-slotted channel hopping as defined by Part 15.4, Low-Rate Wireless Personal Area Networks (LR-WPANs), IEEE 802.15.4e, 2012. Channel hopping schemes are used for various applications for example, Wi-SUN Alliance has proposed a Field Area Network (FAN) specification that specifies the use of channel hopping for smart grid applications.
Existing channel hopping schemes have following requirements:                The next channel in frequency hopping sequence must be at least pseudo random.        All channels must be equally distributed.        The random sequence must be repeatable so that it can be communicated to receivers.These channel hopping schemes do not account for Inter Channel Interference (“ICI”). When a channel is not suitable for transmission due to interference, then typically it affects the data packet transmission in adjacent channels or even a few channels adjacent to it as well. Some of the commonly known random sequences for channel hopping mechanism are Linear Feedback Shift Register (LFSR) and Linear Congruential Generator (LCG).        
These schemes generate pseudo random sequences; however, they do not account for inter channel interference. Although the sequences are random, they do allow for next channels in the list to be close to the current channel, for example, if a packet is dropped due to bad channel conditions, then the possibility is that the retransmission may occur in a channel that is closer to the previous channel and the retransmission may also fail due to the inter channel interference from the previous channel. Most wireless systems have retransmission limits for transmission efficiency purposes and if a packet retransmission reaches the maximum limit for retransmission, then the entire transmission session has to be restarted. This results in multiple transmission sessions and causes waste of system resources and poor bandwidth utilization.
Referring to FIG. 1, an example of a conventional implementation of a Linear Feedback Shift Register scheme is illustrated. The example illustrates the percentage of adjacent channel interference across a number of channel hopping separations (Nsep) for a LFRS sequence when the number of retransmissions limit is set to 6. The amount of adjacent channel interference in the sequence was computed by measuring the number of channels in a sequence that are within Nsep distance from the previous “retransmission count” channels. As illustrated, when the Nsep is increased, the percentage of adjacent channel interference increases exponentially.